Will using the "pre-outs" of an integrated to drive a basic power amp provide sound quality EQUAL to a separate quality pre-amp??It could. But only if the built-in preamp section of the integrated was equal to or better than the separate pre-amp you may be considering.
The power amp, external or the built-in one of the integrated can only receive the best signal that pre-amp in the integrated is capable of sending. So without knowing exactly what models we are dealing with, the answer to your question is just a "maybe".